This Phase I study is designed to assess the safety and maximum tolerated dose of recombinant interleukin-12 (rhIL-12) administered by intravenous injection in patients with advanced malignancies. It will also evaluate the serum concentrations of rhIL-12 following administration as an intravenous injection and levels to the pharmacodynamic immunopharmacology profile of rhIL-12, the anti-tumor efficacy of this dosage schedule and route of administration will be evaluated as a secondary end point measure.